全文获取类型
收费全文 | 1284篇 |
免费 | 33篇 |
国内免费 | 21篇 |
专业分类
化学 | 131篇 |
晶体学 | 3篇 |
力学 | 15篇 |
综合类 | 4篇 |
数学 | 1039篇 |
物理学 | 146篇 |
出版年
2023年 | 2篇 |
2022年 | 7篇 |
2021年 | 2篇 |
2020年 | 8篇 |
2019年 | 39篇 |
2018年 | 44篇 |
2017年 | 14篇 |
2016年 | 8篇 |
2015年 | 25篇 |
2014年 | 45篇 |
2013年 | 81篇 |
2012年 | 49篇 |
2011年 | 90篇 |
2010年 | 69篇 |
2009年 | 85篇 |
2008年 | 97篇 |
2007年 | 92篇 |
2006年 | 100篇 |
2005年 | 59篇 |
2004年 | 44篇 |
2003年 | 25篇 |
2002年 | 31篇 |
2001年 | 18篇 |
2000年 | 24篇 |
1999年 | 38篇 |
1998年 | 27篇 |
1997年 | 25篇 |
1996年 | 33篇 |
1995年 | 23篇 |
1994年 | 16篇 |
1993年 | 27篇 |
1992年 | 13篇 |
1991年 | 14篇 |
1990年 | 8篇 |
1989年 | 8篇 |
1988年 | 1篇 |
1987年 | 2篇 |
1986年 | 2篇 |
1985年 | 6篇 |
1984年 | 4篇 |
1983年 | 2篇 |
1982年 | 4篇 |
1981年 | 6篇 |
1980年 | 3篇 |
1979年 | 7篇 |
1978年 | 5篇 |
1977年 | 2篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1974年 | 1篇 |
排序方式: 共有1338条查询结果,搜索用时 31 毫秒
51.
Christian Mazza 《Probability Theory and Related Fields》1999,113(2):171-190
We consider the ±J spin glass on a finite graph G=(V,E), with i.i.d. couplings. Our approach considers the Z
2 local gauge invariance of the system. We see the gauge group as a graph theoretic linear code ? over GF(2). The gauge is fixed by choosing a convenient linear supplement of ?. Assuming some relation between the disorder parameter
p and the inverse temperature of the thermal bath β
pb
, we study percolation in the random interaction random cluster model, and extend the results to dilute spin glasses.
Received: 5 May 1997 / Revised version: 9 April 1998 相似文献
52.
Andrei E. Vityaev 《Journal of Geometric Analysis》1999,9(1):161-173
We study uniqueness of an H∞ optimization problem which is central to the worst case frequency domain system design. It was known that if the so-called
sublevel sets are strictly convex inC
N, then the uniqueness holds. On the other hand, there are examples of non-uniqueness if the sublevel sets are just strictly
pseudoconvex.
In this paper we prove that uniqueness holds for a type of convexity which is strictly in-between geometric and pseudoconvexity. 相似文献
53.
In this paper we prove that thek-ary fragment of transitive closure logic is not contained in the extension of the (k–1)-ary fragment of partial fixed point logic by all (2k–1)-ary generalized quantifiers. As a consequence, the arity hierarchies of all the familiar forms of fixed point logic are strict simultaneously with respect to the arity of the induction predicates and the arity of generalized quantifiers.Although it is known that our theorem cannot be extended to the sublogic deterministic transitive closure logic, we show that an extension is possible when we close this logic under congruence.Supported by a grant from the University of Helsinki. This research was initiated while he was a Junior Researcher at the Academy of FinlandThis article was processed by the author using the LATEX style filepljourlm from Springer-Verlag. 相似文献
54.
The condition on the offspring distribution in the critical multitype Bienaymé-Galton-Watson process without variance, which was previously shown to be sufficient for the existence of the analogue of the exponential limit law, is now shown also to be necessary. This completely extends previous one-type work of R. S. Slack. 相似文献
55.
Erik A. van Doorn 《Stochastic Processes and their Applications》1981,11(3):261-271
Conditions are obtained for the truncated birth-death process to be stochastically monotone in the long run. 相似文献
56.
Let T = T(A, D) be a self-affine attractor in
defined by an integral expanding matrix A and
a digit set D. In the
first part of this paper, in connection with canonical number systems,
we study connectedness of T when
D corresponds to the set of
consecutive integers
. It is shown that in
and
, for any integral expanding matrix A, T(A, D) is connected.
In the second part, we study connectedness of Pisot dual tiles, which
play an important role in the study of
-expansions, substitutions and
symbolic dynamical systems. It is shown that each tile of the dual
tiling generated by a Pisot unit of degree 3 is arcwise connected. This
is naturally expected since the digit set consists of consecutive
integers as above. However surprisingly, we found families of
disconnected Pisot dual tiles of degree 4. We even give a simple
necessary and sufficient condition of connectedness of the Pisot dual
tiles of degree 4. Detailed proofs will be given in [4].
Received: 2 March 2003 相似文献
57.
Piaoping Yang Zhenlü Wang JianFeng Yu Qingsheng Liu Tonghao Wu 《Reaction Kinetics and Catalysis Letters》2004,83(1):129-136
A kinetic model is proposed to account for the effect of oxygen during catalyst premodification on the rate and enantioselectivity in hydrogenation of methyl pyruvate over cinchonidine modified platinum catalysts.This revised version was published online in December 2005 with corrections to the Cover Date. 相似文献
58.
Béla?BollobásEmail author David?Gamarnik Oliver?Riordan Benny?Sudakov? 《Combinatorica》2004,24(2):187-207
Consider a complete graph on n vertices with edge weights chosen randomly and independently from an exponential distribution with parameter 1. Fix k vertices and consider the minimum weight Steiner tree which contains these vertices. We prove that with high probability the weight of this tree is (1+o(1))(k-1)(log n-log k)/n when k =o(n) and n.* Research supported in part by NSF grant DSM9971788 Research supported in part by NSF grants DMS-0106589, CCR-9987845 and by the State of New Jersey. Part of this research was done while visiting IBM T. J. Watson Research Center. 相似文献
59.
The Diameter of a Scale-Free Random
Graph 总被引:1,自引:0,他引:1
We consider a random graph process in which vertices are
added to the graph one at a time and joined to a fixed number
m of earlier vertices, where
each earlier vertex is chosen with probability proportional to
its degree. This process was introduced by Barabási and Albert
[3], as a simple model of the growth of real-world graphs such
as the world-wide web. Computer experiments presented by
Barabási, Albert and Jeong [1,5] and heuristic arguments given
by Newman, Strogatz and Watts [23] suggest that after
n steps the resulting graph
should have diameter approximately logn. We show that while this holds for
m=1, for
m2 the diameter is
asymptotically log n/log
logn.* Research supported in part by NSF grant no.
DSM9971788 相似文献
60.
The goal of the paper is to initiate research towards a general, Blow-up Lemma type embedding statement for pseudo-random graphs with sublinear degrees. In particular, we show that if the second eigenvalue of a d-regular graph G on 3n vertices is at most cd
3/n
2 log n, for some sufficiently small constant c > 0, then G contains a triangle factor. We also show that a fractional triangle factor already exists if < 0.1d
2/n. The latter result is seen to be best possible up to a constant factor, for various values of the degree d = d(n).* Supported by a USA-Israeli BSF grant, by a grant from the Israel Science Foundation and by a Bergmann Memorial Award. Research supported in part by NSF grants DMS-0106589, CCR-9987845 and by the State of New Jersey. Research supported in part by NSF grant DMS 99-70270 and by the joint Berlin/Zurich graduate program Combinatorics, Geometry, Computation, financed by the German Science Foundation (DFG) and ETH Zürich. 相似文献